The present invention relates generally to methods for manufacturing and polishing fiber optic components. More particularly, the present invention relates to methods for polishing fiber optic attenuator ferrules.
Fiber optic attenuators are optical components that induce a calibrated loss between two connectors to dampen (i.e., attenuate) an optical signal. Attenuation is desirable if the optical signal has a power level that exceeds the operating range of the equipment to which the signal is being transferred. Excessive signal power can cause saturation at the receiver and induce system errors and failures. Attenuation is typically achieved by passing the signal through an absorption filter or an air gap. Conventional fiber optic attenuators are available in bulkhead, in-line and build-out configurations.
FIGS. 1 and 2 illustrate a prior art in-line attenuator 20. The attenuator 20 includes a ferrule assembly 22 mounted within a housing 24. The ferrule assembly 22 includes a ferrule structure 26 having a first end face 28 accessible from a first end 29 of the housing 24, and a second end face 30 accessible from a second end 31 of the housing 24. The ferrule assembly 22 also includes a hub 32 located at a mid-region of the ferrule structure 26. The hub 32 nests within a hub receiver 33 defined by the housing 24. An attenuating structure (e.g., an absorption filter or air gap) is located within the ferrule structure 26.
FIG. 3 shows the attenuator 20 providing an optical coupling between first and second fiber optic connectors 40 and 50. In FIG. 3, a cover 61 (shown in FIG. 1) at the first end 29 of the housing 24 has been pivoted open to expose the first end face 28. The first connector 40 is inserted over the first end 29 of the housing 24, and the second connector 50 is inserted within the second end 31 of the housing 24. The first connector 40 includes a ferrule 42 having an end face 43 that abuts against the end face 28 of the ferrule structure 26 when the connector 40 is coupled to the attenuator housing 24. The second connector 50 includes a ferrule 52 having an end face 53 that abuts against the end face 30 of the ferrule structure 26 when the connector 50 is coupled to the attenuator housing 24. In use, optical signals are transferred between the connectors 40, 50 by passing through the ferrule assembly 22. As the signals pass through the ferrule assembly 22, the desired attenuation is provided.
To improve performance parameters such as insertion loss and return loss, it is desirable to polish the end faces 28, 30 of the ferrule structure 26. It is preferred for the end faces 28, 30 to be polished at a slight angle (e.g., about 8 degrees relative to a plane perpendicular to a longitudinal axis of the ferrule). To ensure acceptable performance levels, it is preferred for the angled end faces 28, 30 of the ferrule/hub assembly 22 to abut angled end faces 43, 53 of the connector ferrules 42, 52 in a generally parallel relationship as shown in FIG. 3. Slight deviations in the relative orientations of the end faces can result in air gaps between the end faces 28, 43 and 30, 53 (see FIG. 4 where misalignment is shown between the end faces 28 and 43). This type of misalignment can be detrimental to the optical performance of the coupling.
In the prior art, the end faces 28 and 30 of the ferrule structure 26 are typically polished prior to mounting the ferrule assembly 22 in the housing 24. One reason for this practice is because the end face 30 of the ferrule structure 26 is not accessible for polishing once the ferrule structure 26 has been mounted within the attenuator housing 24. However, it has been determined that when the ferrule assembly 22 is mounted within the housing 24 after the end faces 28, 30 have already been polished, part tolerances mismatches can cause the end faces 28, 30 to be slightly rotationally offset from their intended rotational orientations. With the end faces 28, 30 rotationally offset from their intended orientations, the end faces 28, 30 may not make parallel contact with the connector end faces 43, 53 when the connectors 40, 50 are coupled to the attenuator 20. As indicated above, this type of misalignment can be detrimental to the optical performance of the coupling.
The present disclosure relates to methods for ensuring the proper rotational alignment of a ferrule within a housing. It will be appreciated that the specific method steps disclosed herein are examples of one way the broad concepts of the present invention may be put into practice, and that variations can be made with respect to the described method steps without departing from the broad scope of the inventive concept.